As oil and gas reserves have been discovered in deeper water, attempts have been made by the oil industry to improve the cost effectiveness of offshore platforms without sacrificing their operational reliability and safety. For deep water operations, such as in water depths of 1000 feet, structural costs generally become more important factors of total field development costs than drilling, topside and transportation costs which dominate in shallow water operations.
In recent years, there have been advances in the availability of offshore construction equipment for large platforms. Such equipment has helped to extend water depth ranges of fixed based jackets to well beyond 1000 feet. Fixed based jackets are a proven base for conventional drilling and production; however, the cost for a structure itself in 1000 feet of water is often on the order of $100 to $150 million dollars, not including topside facilities, drilling or pipelines. This places a heavy economic burden on most oil and gas prospects in the Gulf of Mexico.
There is a clear need for more cost-effective platforms in greater water depths at which conventional drilling and production operations can be maintained with proven components with less material. This need will increase in coming years if fabrication yards are filled and the unit prices of steel fabrication continue to rise. The present invention provides a compliant jacket which fulfills this need and provides a cost savings of 20% to 30% over that achieved with fixed based jackets.